A thermal flow meter which detects a flow rate by performing heat transfer with a measurement target gas is widely used since the measurement accuracy is higher than that of other types of flow meters. The thermal flow meter has a bypass passage, which takes a part of the measurement target gas flowing through a main passage, flows the taken measurement target gas therein, and is formed of a resin, and a flow rate detection circuit which is used for detecting the flow rate of a gas by performing heat transfer with the measurement target gas flowing through the bypass passage and enveloped by a resin.
In the prior art, a hole is formed in the bypass passage formed of a resin, the flow rate detection circuit covered with a resin is inserted into the hole, and a gap between the hole and the resin covering the flow rate detection circuit is filled with an elastic adhesive. Such a technique is disclosed in Japanese Patent Laid-Open Publication No. 2011-252796 (Patent Literature 1).